U.S. patent application number 14/113092 was filed with the patent office on 2014-02-13 for equipment for inserting a joint prosthesis, in particular a knee prosthesis.
This patent application is currently assigned to DERU GMBH. The applicant listed for this patent is Balzarini Amos, Klaus Dmuschewsky, Marco Iredi. Invention is credited to Balzarini Amos, Klaus Dmuschewsky, Marco Iredi.
Application Number | 20140046331 14/113092 |
Document ID | / |
Family ID | 44275912 |
Filed Date | 2014-02-13 |
United States Patent
Application |
20140046331 |
Kind Code |
A1 |
Amos; Balzarini ; et
al. |
February 13, 2014 |
EQUIPMENT FOR INSERTING A JOINT PROSTHESIS, IN PARTICULAR A KNEE
PROSTHESIS
Abstract
Equipment for inserting a joint prosthesis, in particular a
femur component of a knee prosthesis, comprises a base frame having
a guiding plate and a laterally protruding primary gage, a
fastening device on the bone, and a curved milling gage having a
main body and a guiding piece, which can be moved along a curved
guiding path relative to the main body and has a receptacle for an
abrasive tool. Furthermore, the equipment comprises an aligning
device, which places the curved milling gage in a clearly defined
relative position when the curved milling gage is inserted into the
base frame. Due to the precise positioning in conjunction with the
curved guiding path, the mounting seat can be prepared easily
without damaging surrounding tissue. Thus, even large and complexly
shaped prostheses, such as knee joint prosthesis, can be
reproducibly inserted in an easy and safe manner.
Inventors: |
Amos; Balzarini;
(Norderstedt, DE) ; Iredi; Marco; (Norderstedt,
DE) ; Dmuschewsky; Klaus; (Hamburg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Amos; Balzarini
Iredi; Marco
Dmuschewsky; Klaus |
Norderstedt
Norderstedt
Hamburg |
|
DE
DE
DE |
|
|
Assignee: |
DERU GMBH
NORDERSTEDT
DE
|
Family ID: |
44275912 |
Appl. No.: |
14/113092 |
Filed: |
April 19, 2012 |
PCT Filed: |
April 19, 2012 |
PCT NO: |
PCT/EP12/57163 |
371 Date: |
October 21, 2013 |
Current U.S.
Class: |
606/80 ;
606/88 |
Current CPC
Class: |
A61B 17/1675 20130101;
A61B 17/1642 20130101; A61B 17/164 20130101; A61B 17/1735 20130101;
A61B 17/154 20130101; A61B 17/1615 20130101; A61B 2017/1602
20130101; A61B 2090/034 20160201; A61B 17/1659 20130101; A61B
17/155 20130101; A61B 17/1764 20130101; A61B 17/144 20161101 |
Class at
Publication: |
606/80 ;
606/88 |
International
Class: |
A61B 17/17 20060101
A61B017/17; A61B 17/16 20060101 A61B017/16 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 21, 2011 |
EP |
11163566.0 |
Claims
1. A set of equipment for inserting a joint prosthesis, at the end
of a bone, comprising: a base frame comprising a guiding plate and
a primary gauge protruding laterally from the guiding plate, a
fastening device for arranging the base frame on the bone in a
fixed position, a curved milling gauge with a main body and a
guiding piece, the guiding piece being movable along a curved
guiding path relative to the main body and comprising a receptacle
for an abrasive tool, and an aligning device which places the
curved milling gauge in a defined relative position when the curved
milling gauge is inserted into the base frame.
2. The set of equipment of claim 1, wherein the curved guiding path
has a non-constant curvature.
3. The set of equipment of claim 1, wherein the guiding piece is
mounted via a follower with the guiding path and via a pivot
bearing pivotably on the main body.
4. The set of equipment of claim 3, wherein the pivot bearing is
arranged at a distance from the follower and has a toggle linkage
mounted pivotably on either side.
5. The set of equipment of claim 4, wherein the toggle linkage is
mounted removably on the main body.
6. The set of equipment of claim 3, wherein the guiding piece is
removable.
7. The set of equipment of claim 6, comprising an angular lock
between the guiding piece and main body that can be separated by
moving the guiding piece into an extension of the guiding path.
8. The set of equipment of claim 7, wherein the angular lock
comprises a pivot bearing sleeve and a non-circular pivot pin,
which only opens in one angular position of the guiding piece.
9. The set of equipment of claim 8, wherein the pivot bearing
sleeve open toward one side via a constriction, the pivot pin
having a meridian of smallest width and a meridian of greatest
width, and the breadth of the constriction is sufficient for the
passage of the meridian of smallest width, but not of greatest
width.
10. The set of equipment of claim 3, wherein the receptacle defines
an axis for the abrasive tool which is arranged at an oblique angle
to the line between the follower and pivot bearing.
11. The set of equipment of claim 10, wherein the receptacle for
the abrasive tool on the guiding piece cooperates with a depth
stop.
12. The set of equipment of claim 11, wherein the depth stop is
formed as a stepped seat in the receptacle.
13. The set of equipment of claim 10, wherein the guiding piece has
a double receptacle for the abrasive tool.
14. The set of equipment of claim 13, wherein the double receptacle
has divergent axes such that the abrasive tool points outwardly in
the inserted state.
15. The set of equipment of claim 3, wherein the guiding piece with
the pivot bearing can be disassembled from one side of the main
body and reassembled on the other side.
16. The set of equipment of claim 1, wherein fastening bores are
provided on one or both of the main body and the guiding path.
17. The set of equipment of claim 1, wherein an aligning insert is
arranged exchangeably on the guiding plate in a defined position
and is configured to receive an aligning body.
18. The set of equipment of claim 17, wherein the receptacle for
the aligning body is open on one side.
19. The set of equipment of claim 1, comprising a frontal-sawing
insert having two kerfs aligned in a V-shaped manner relative to
one another and having a bipolar fastening.
20. The set of equipment of claim 1, comprising spacers at
different heights, configured for arrangement on either side on the
edge of the guiding plate.
21. The set of equipment of claim 1, wherein a first milling insert
can be attached exchangeably to the guiding plate and forms a
defined receptacle for a broach milling cutter.
22. The set of equipment of claim 1, comprising a feeler gauge
which can be plugged into a plug receptacle on the guiding plate in
an accurately angled manner.
23. The set of equipment of claim 1, wherein a second milling
insert can be attached exchangeably to the guiding plate and forms
a double receptacle for receiving a bulk milling cutter in a manner
in which the cutter can be plugged into either receptacle.
24. The set of equipment of claim 1, wherein a second auxiliary
milling insert can be attached exchangeably to the guiding plate
and forms a double receptacle for receiving a bulk milling cutter
in a manner in which the cutter can be plugged into either
receptacle.
25. The set of equipment of claim 1, wherein a third milling insert
can be attached to the guiding plate and forms a slotted link guide
for a depth milling cutter.
26. The set of equipment of claim 25, wherein the slotted link
slider has a handle.
27. The set of equipment of claim 26, comprising a depth stop.
28. The set of equipment of claim 25, comprising a slotted link
window, in which the slotted link slider can be received.
29. The set of equipment of claim 25, wherein the slotted link
guide comprises two guiding levers connected to one another in a
hinged manner, and the receptacle for the depth milling cutter is
arranged at one end and is arranged at the other end pivotably on
an insert on the guiding plate.
30. The set of equipment of claim 1, wherein the guiding plate has
a linear guide, for different inserts.
31. The set of equipment of claim 1, comprising curved milling
gauges in different sizes.
32. The set of equipment of claim 1, comprising a pair of insertion
tongs for the curved milling gauge that engages in a form-fitting
manner in a defined position and cooperates via aligning lugs with
the aligning device such that the curved milling gauge is inserted
in a clear position relative to the guiding plate.
33. The set of equipment of claim 1, comprising aligning rods that
can be arranged laterally on the base frame pointing away from one
another.
34. The set of equipment of claim 1, comprising a drill with depth
stop for creating receptacles of anchoring pins of the joint
prosthesis.
35. The set of equipment of claim 1, comprising different awls for
reaming a concavity on the bone.
36. The set of equipment of claim 1, comprising a rasp/broaching
awl of which the shaft has a recess with a reduced thickness
configured to receive a stop plate.
37. The set of equipment of claim 36, wherein the rasp/broaching
awl has two, three or four cutting edges.
38. The set of equipment of claim 37, wherein teeth are arranged on
the cutting edges with relative vertical offset.
39. The set of equipment of claim 1, comprising an aligning gauge
for positioning the base frame that can act on the aligning
device.
40. The set of equipment of claim 1, wherein the joint prosthesis
comprises a femur component of a knee prosthesis and the bone
comprises in the femur.
41. The set of equipment of claim 2, wherein the non-constant
curvature changes continuously along the guiding path.
42. The set of equipment of claim 2, wherein the respective center
of curvature moves dorsally over a path from 2 to at most 6 mm.
43. The set of equipment of claim 10, wherein the angle lies in the
range between 10 and 35 degrees.
44. The set of equipment of claim 10, wherein the angle lies is the
range between 15 and 30 degrees.
45. The set of equipment of claim 12, wherein the stepped seat is
open toward one side.
46. The set of equipment of claim 17, wherein the aligning body
comprises a bone broaching tool.
47. The set of equipment of claim 21, wherein the receptacle holds
the milling cutter in a position and forms a depth stop.
48. The set of equipment of claim 23, wherein the double receptacle
has different depth stops and lateral offset.
49. The set of equipment of claim 24, wherein the double receptacle
has one or both of identical depth stops and no lateral offset.
50. The set of equipment of claim 25, wherein the depth milling
cutter is received in a slotted link slider.
51. The set of equipment of claim 27, wherein the depth stop
cooperates with the depth milling cutter and a second depth milling
cutter such that different milling depths are achieved.
52. The set of equipment of claim 30, wherein the linear guide
comprises a dovetail guide.
53. The set of equipment of claim 35, wherein the concavity
comprises a medullary cavity on the femur.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a national stage application under 35
USC 371 of International Application No. PCT/EP2012/057163, filed
Apr. 19, 2012, which claims the priority of European Application
No. 11 163 566.0, filed Apr. 21, 2011, the entire contents of which
are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention relates to a set of equipment for inserting a
joint prosthesis, in particular a femur component of a knee
prosthesis, at the end of a bone, in particular the femur.
BACKGROUND OF THE INVENTION
[0003] The implantation of a modern joint prosthesis, in particular
a knee prosthesis, is a challenging task for the surgeon. Joint
prostheses of this type have to reproduce the complex physiological
path of movement of the natural joint in a highly lifelike manner.
This requires not only highly developed prostheses, but also
precise implantation of the joint prosthesis. Only in this way can
it be ensured that the desired functionality of the natural joint
can be correctly restored. It goes without saying that, to ensure
sufficient success of the therapy, the prosthesis has to be
positioned not only precisely, but also safely and reproducibly. In
particular, the surrounding tissue, in particular surrounding bone
material, must not be damaged or injured, since this tissue in many
cases plays a significant role for the supporting function.
Particularly in view of a long service life of the joint
prosthesis, there is a conflict of objectives however. On the one
hand, it is favorable for the long service life if forces are
transmitted over a large area. On the other hand, a design with a
large area that thus leads to dimensions of the prosthesis that are
too large on the whole may result however in an increased spatial
requirement and may therefore easily result in damage to
surrounding tissue. There is thus a risk that material will be
removed in incorrect areas in particular important for supporting
the joint prosthesis. It is therefore necessary to carry out the
implantation on the basis of exact position references.
[0004] The equipment known from the relevant prior art indeed
enables tried and tested implantation of the joint prosthesis, in
particular of a knee joint prosthesis. However, it presupposes
considerable experience on the part of the surgeon, since the
equipment itself only provides little assistance in respect of
correct positioning.
SUMMARY OF THE INVENTION
[0005] In order to avoid harmful effects on the patient caused by
erroneous positioning or by removal of too much natural bone
substance, an object of the present invention is to create an
improved set of equipment which enables more precise
implantation.
[0006] This is achieved in accordance with the invention by a set
of equipment as broadly described herein. Advantageous developments
are disclosed in the detailed embodiments described below.
[0007] With a set of equipment for inserting a joint prosthesis, in
particular a femur component of a knee prosthesis, at the end of a
bone, in particular the femur, a base frame that has a guiding
plate and a primary gauge protruding laterally therefrom, a
fastening device for arranging the base frame on the bone in a
fixed position, and a curved milling gauge with a main body and a
guiding piece are provided in accordance with the invention, the
guiding piece being movable along a curved guiding path relative to
the main body and having a receptacle for an abrasive tool, and an
aligning device, which places the curved milling gauge in a clearly
defined relative position when the curved milling gauge is inserted
into the base plate.
[0008] The invention is based on the concept of creating, by means
of a base frame which is positioned in a manner known per se in a
fastening device on the bone, a stable platform which is highly
accurate by means of the aligning device and at which the curved
milling gauge can be easily inserted and at the same time is
aligned automatically and safely in a precise manner. The curved
milling gauge has a curved guiding path, along which, by means of
the abrasive tool, the bone can be shaped accordingly in a rounded
manner. This is suitable in particular for preparation of a
receiving seat for condyle components of the knee joint prosthesis.
The complicated shape of these components can be produced easily
and yet precisely by the surgeon thanks to the invention by means
of a forced guidance, as is achieved in accordance with the
invention by the curved guiding path of the curved milling gauge.
Thanks to the forced guidance of the abrasive tool, deviations in
the shape are hardly possible, even under unfavorable operating
conditions. Not only is the prepared receiving seat thus created
therefore highly accurate in terms of shape, but it is also
ensured, with correct basic alignment of the base frame, which, via
the aligning device, clearly determines the positioning of the
curved milling gauge, that surrounding tissue is not injured or
damaged, and in particular that no adjacent bone material is
unnecessarily removed, which may be required to support the
prosthesis. In particular, a wall-like bone residue can thus be
left on the patella in the case of knee joint prostheses and not
only provides a base for the patella-side support of the joint
prosthesis, but also serves as a delimitation, acting frontally, of
the box-shaped hollow of the medullary cavity for receiving the
main body of the prosthesis.
[0009] In short, the invention, on the basis of a clean basic
positioning, enables an exactly defined removal of bone material,
wherein even complicated shapes, such as the varying curvature of
the condyles in the case of a knee joint, can be developed easily
and in a positionally accurate manner.
[0010] In particular for adaptation to the curvature of the
condyles, which is not constant as already mentioned above, it is
expedient if the curved guiding path of the curved milling gauge
changes continuously in terms of its curvature along its extent.
With such a change in curvature, the natural path of movement of
the knee is reproduced as accurately as possible in terms of
function. Here, the geometries are preferably selected such that
the respective center of curvature remains in one plane over the
non-constant curvature along the guiding path, wherein it shifts in
a horizontal direction from front to rear (preferably by 10 mm, at
most 20 mm). The generation of a complicated curve progression with
varying curvature, wherein the position of the center of curvature
is also to meet specific requirements, is difficult using the
previous equipment and is hardly or even not at all assisted
thereby. In this case, the focus in the prior art was rather on the
experience and skill of the surgeon alone or primarily. With the
equipment according to the invention, it is ensured that a precise
shaping of the curve progression in accordance with the
specifications can always be achieved.
[0011] In order to achieve this, the guiding piece, in which the
abrasive tool is received, is expediently mounted both via a
follower with the guiding path and via a pivot bearing pivotably on
the main body. With this twofold mounting, both the rotation of the
guiding piece along the guiding path is controlled, and also the
alignment of the guiding piece relative to the guiding path. Both
the radius of curvature and also the position of the center of the
curvature can therefore be controlled precisely. It has proven to
be particularly useful if the pivot bearing is arranged at a
distance from the follower and has a toggle linkage mounted
pivotably on either side. In this case, a space-saving kinematics
is produced, which additionally combines precise guidance with an
avoidance of cases of jamming. The latter in particular is a
significant aspect, since blocking may easily occur in the
operating environment, especially with highly precise, guided
technical devices, due to the omnipresent risk of foreign body
infiltration (in particular tissue residues or bodily liquids). The
combination of a follower with a toggle linkage mounted pivotably
on either side is robust in this respect.
[0012] It is particularly preferable if the toggle linkage is
mounted removably on the main body via a securing device. This
makes it possible to insert the curved milling gauge via its main
body separately into the base plate, without this being impeded
during this process by the guiding piece movable over a large
adjustment range. This not only constitutes a simplification, but
enables improved handling. This is true specifically also for the
case when, due to low tolerances, the insertion of the curved
milling gauge is difficult, wherein the force necessary for this
purpose may be applied using a hammer where necessary. Thanks to
the fact that the guiding piece can be removed, there is then no
risk when the main body is driven in of damaging the guiding path
of the guiding piece, which is key for accurate positioning.
[0013] In order to avoid a cumbersome assembly of the guiding piece
in the operating environment and also to preclude the risk of a
loss of individual assembly parts, a quick-action coupling is
expediently provided between the guiding piece and main body. An
embodiment as an angular lock, which can be separated by moving the
guiding piece into an extension of the guiding path, has proven to
be particularly expedient. In this case, an extension is understood
to mean a region of the guiding path that is not necessary for the
actual forming by means of the abrasive tool (but constitutes an
additional region that is unused so to speak). By bringing the
guiding piece into this extension, the angular lock reaches such a
position in which it can be easily separated without tools. The
same is true for the assembly process, which similarly can be
carried out easily and without tools. For this purpose, the guiding
piece needs to be brought merely into the extreme position in the
extension so as to then be separated or refitted. In the region of
the extension, this is expediently identified in that an opening of
the guiding path outwardly is provided there. This opening is not
absolutely necessary, but facilitates a removal of the guiding
piece in this position. It goes without saying that this opening is
not provided accordingly in the rest of the region of the guiding
path belonging to the extension.
[0014] The angular lock may consist of a pivot bearing sleeve and a
non-circular pivot pin, which is formed such that the angular lock
opens only in one angular position of the guiding piece. This is
achieved in that the pivot bearing sleeve is open toward one side
via a constriction. The non-circular pivot pin is created such that
it has different widths depending on positioning. This width in a
specific positioning is referred to as the width in a specific
meridian. If the non-circular pivot pin thus has such a shape that
corresponds substantially to a rectangle with short
circular-arc-shaped sides, the width in the meridian of smallest
breadth is thus equal to the distance between the two long sides of
the rectangle, and the width corresponding to the meridian of
greatest breadth is equal to the length of the longer side of the
rectangle plus the convex curvatures provided by the
circular-arc-shaped short sides. Since the constriction is selected
such that it is sufficient for the passage of the pivot pin in its
meridian of smallest width, but is not sufficient for the passage
in a meridian of greatest width, the guiding piece with its pivot
pin can be removed merely in one such orientation in which the
pivot pin can pass the constriction with its meridian of smallest
width. In accordance with the invention, this is then only the case
when the guiding piece is located in the position of the guiding
path which belongs to the extension. In the other positions on the
guiding path, the guiding piece is locked, since there the width of
the pivot pin is greater than the breadth of the constriction, such
that the pivot pin cannot be removed through the constriction. A
simple and robust quick-action coupling, which is controlled in an
angle-based manner and therefore provides the guarantee that the
separation can only occur in one specific position, is thus
produced. The guiding piece is likewise assembled easily, since it
only has to be inserted in the correct position into the extension
of the guiding path, wherein the pivot pin with its meridian of
smallest width is readily guided through the constriction into the
pivot bearing sleeve. A simple locking mechanism, without tools, is
thus achieved by inserting the guiding piece into its position.
[0015] The toggle linkage is preferably likewise removably mounted
on the main body. It is thus made possible to remove all movable
parts. This is not only favorable for the cleaning of the
equipment, but also, as already mentioned, for the assembly of the
main body in difficult cases, without resulting in damage to the
sensitive guiding devices. The toggle linkage is preferably mounted
via a securing device, such that it is protected against unintended
detachment from the intended position. In particular, a screw has
proven to be an expedient securing device.
[0016] By means of its mounting, the guiding piece movable along
the guiding path defines an axis for the abrasive tool. The axis
can be oriented such that it is arranged in the pivot plane of the
guiding piece, but is preferably at an oblique angle. This axis is
further preferably likewise arranged at an oblique angle to the
line between follower and pivot bearing. For this purpose, a range
between 10.degree. and 35.degree., further preferably between
15.degree. and 30.degree., has proven to be expedient. A bend
reserve is thus created at the toggle linkage and also allows
continuous change of the radius along the course of the guiding
path.
[0017] The receptacle for the abrasive tool on the guiding piece
preferably cooperates with a depth stop. In this case, a depth stop
is understood to mean a device which delimits the penetration depth
of the abrasive tool into the workpiece, that is to say in this
case the bone on which the equipment according to the invention is
used. An embodiment of the depth stop in such a way that it is a
stepped seat, which is preferably open toward one side, has proven
to be expedient. As a result of the graduation, a thickening
arranged accordingly on the deep miller rests thereon and thus
forms a stop with respect to the penetration depth of the
supporting tool. The lateral opening ensures that the abrasive tool
can be inserted into the receptacle directly from the side, without
having to be threaded in a cumbersome manner.
[0018] In principle, it is indeed sufficient to provide just one
receptacle on the guiding piece, however it is advantageous
particularly for knee prostheses if a double receptacle is formed
on the guiding piece in order to form two condyles. The abrasive
tool can thus be changed over once one condyle is formed in order
to thus form the second condyle at the other position. A
disassembly or a changeover of the curved milling gauge is
therefore not necessary, and therefore the precise positioning is
maintained.
[0019] It has proven to be expedient if the double receptacle is
formed on the guiding piece such that divergent axes are produced.
In this case, divergent is understood to mean that the cutting head
of the abrasive tool points outwardly in the inserted state. The
condyles can thus be provided with a physiological inclination,
which assists a self-centering function present in the natural knee
joint.
[0020] The double receptacle is not absolutely necessary however.
It may also be possible to disassemble the guiding piece with the
pivot bearing, and where applicable, with the toggle linkage from
one side of the main body and to reassemble it on the other side.
The condyle can thus be prepared initially on one side, and, after
reassembly on the other side with the same receptacle on the
guiding piece, the other condyle can be prepared. Since in this
case the positioning of the curved milling gauge with its main body
also does not have to be changed per se, the precise positioning is
maintained.
[0021] Fastening bores are expediently provided on the main body
and/or the guiding path. They enable a securing of the positioning
of the curved milling gauge, more specifically independently of its
entry into the base plate. The fastening security and therefore
ultimately also the quality of the positioning accuracy are
therefore increased; in particular it is made possible to remove
the base frame.
[0022] In accordance with a specific aspect of the invention, which
may also be worthy of independent protection, various inserts for
the base frame are provided. An aligning insert may thus be
provided exchangeably on the base frame, said aligning insert being
designed to receive an aligning body in a defined position. The
aligning body may in particular be a bone broaching tool, in
particular an awl or a rasp for opening the medullary cavity.
[0023] The guiding piece described in previous paragraphs is
usually formed such that the axis of the receptacle for the
abrasive tool is oriented such that the axis has a radial
orientation. This means that it is directed substantially toward
the center of curvature. Alternatively, the axis may also be
oriented transverse to the plane defined by the curvature. This
provides the advantage that the abrasive tool can be inserted into
the receptacle from the side. With a sufficiently large abrasive
tool, two condyle shapes can thus be formed on a femur with a
movement along the guiding path. However, a variant is preferred in
which the guiding piece with the pivot bearing and, where
applicable, the toggle linkage can be disassembled from one side of
the main body and reassembled on the other side. In this case, the
abrasive tool is dimensioned such that only one condyle path,
specifically the closest, is formed. This provides the advantage of
more precise control and also makes it possible to provide an
inclination due to a possibly slightly tilted axis in the
receptacle of the guiding piece of the condyle path. A result
comparable to that which can be achieved with the divergent axes in
the above-described guiding piece having a double receptacle is
thus obtained.
[0024] In order to achieve an independent fastening of the curved
milling gauge to the bone to be machined, fastening bores may
expediently be provided on the main body and/or the guiding path.
They are used primarily as a replacement for the fastening by means
of the orienting device to the base frame anchored in the bone,
such that the base frame can be removed as required.
[0025] In accordance with a further aspect of the invention, which
may be worthy of independent protection, an ensemble of inserts are
provided for the base frame and can be received exchangeably in the
guiding plate. In this case, the inserts may be formed in
particular by an aligning insert, a frontal-sawing insert, a first
milling insert, a second milling insert, and a third milling insert
with a slotted link guide.
[0026] The aligning insert is designed so as to be arranged
exchangeably in a defined position on the guiding plate and has a
receptacle for the aligning body. The base plate can therefore be
clearly positioned with respect to the aligning body. The aligning
insert is expediently side-dependent, that is to say there is an
aligning insert "L" for implantation of the left-side prosthesis
and an aligning insert "R" for the implantation of a right-side
prosthesis. It is noted that a symmetrical auxiliary aligning
insert, which can therefore be used similarly on either side, may
also be provided additionally as supplements.
[0027] The receptacle for the aligning body on the aligning insert
is expediently open on one side. This is preferably implemented by
means of a constriction. The aligning body (this generally being
here an implement inserted into the medullary cavity of the bone,
such as an awl or a milling cutter) can thus be easily inserted
into the receptacle and removed therefrom from the side.
[0028] The ensemble of inserts further comprises a frontal-sawing
insert. This has two kerfs aligned in a V-shape relative to one
another and a bipolar fastening. The bipolar fastening is
understood to mean a fastening which defines two alternative
fastening positions. These fastening positions are selected such
that the kerfs are arranged in one case for implantation of a
left-side prosthesis and in the other case for implantation of a
right-side prosthesis. An expedient embodiment for such a bipolar
fastening may be two individual fastening bores, or preferably a
slot, of which the end points define the respective bipolar
fastening positions.
[0029] The set of equipment preferably comprises further spacers
for different heights, which are designed for arrangement on either
side at the edge of the guiding plate. A specific distance of the
guiding plate from the bone can be adjusted by means of the
spacers. This is suitable in particular for cases in which bone
material has already been removed due to a prior operation. It is
thus possible to compensate for the material loss. Spacers having
different dimensions are preferably contained in the set of
equipment.
[0030] The ensemble further comprises a first milling insert, which
can be attached exchangeably in the guiding plate. It forms a
defined receptacle for a broach milling cutter, said receptacle
preferably also forming a depth stop for the broach milling cutter.
It is thus ensured that the milling process is carried out in a
precise manner. In particular, the broach milling cutter therefore
does not drift to the side and therefore remove bone material
laterally or frontally or dorsally in an undesired manner. The
depth stop further ensures that bone material is removed only in
the depth necessary for implantation. The distance between the
receptacle and the primary gauge is dimensioned such that, when the
broach milling cutter is inserted, a distance remains which
corresponds to the thickness of a wall that is to be left on the
frontal side of the patella. This is achieved thanks to the forced
guidance thus achieved of the broach milling cutter, even in a
confusing operating environment, more specifically including a less
experienced surgeon.
[0031] The set of equipment preferably further comprises a feeler
gauge, which can be attached at a precise angle to a plug
receptacle on the base frame. The position of the pivot point of
the prosthesis can be indicated by means of this feeler gauge, more
specifically preferably in two orientation planes.
[0032] The ensemble further comprises a second milling insert,
which can be attached exchangeably to the guiding plate. This has a
double receptacle for receiving a bulk milling cutter in a manner
in which the cutter can be plugged into either receptacle. In this
case, the double receptacle is preferably formed such that it has
different depth stops and additionally a lateral offset. In this
case, a lateral offset is understood to mean that the bulk milling
cutter, in one position of the double receptacle in the
lateral/medial direction, is positioned differently than in the
other position of the double receptacle. The same is true with
respect to the depth stop, specifically the fact that the bulk
milling cutter, in one of the two positions, reaches a greater
milling depth than in the other position. The double receptacle is
preferably formed such that its regions overlap. After the milling
process, an associated hollow is thus produced in the bone. This
forms the basis for further development so as to be able to produce
a defined shape for precise implantation. A space of maximum size
can therefore be milled out without at the same time posing the
risk of injuring the surrounding bone wall.
[0033] It is noted that an auxiliary milling insert which likewise
has a double receptacle may also be provided as a second milling
insert. This double receptacle is simplified however in the sense
that it preferably has stops of identical depth and/or has no
lateral offset. Simpler structures for the hollow can therefore be
produced. This auxiliary milling insert is then in particular
expedient if only a relatively small hollow has to be
developed.
[0034] The ensemble further comprises a third milling insert, which
can be attached to the guiding plate. This forms a slotted link
guide for a depth milling cutter, which is preferably received in a
slotted link slider. With the slotted link guide, the hollow can be
formed finely by means of the depth milling cutter. The slotted
link in this case delimits the movement of the depth milling cutter
in the lateral/medial direction. Furthermore, the movement of the
milling cutter in the frontal/dorsal direction is limited by means
of a slotted link window. The slider preferably has a handle, which
surrounds the depth milling cutter coaxially. The depth cutting
miller can therefore be guided more precisely. The slotted link
guide may further have windows in order to visually check the
milling process.
[0035] The slotted link guide preferably has a depth stop. A second
depth milling cutter may thus also be provided, such that two
different milling depths are defined. This enables safe and more
precise development, even of complex hollows.
[0036] In accordance with an alternative embodiment, the slotted
link guide may also comprise two guiding levers connected to one
another in a hinged manner. In this case, the receptacle for the
depth milling cutter may be arranged at one end, whereas a
pivotable mounting on the insert in the guiding plate is provided
at the other end of the guiding levers interconnected in a hinged
manner. The milling cutter is thus guided more precisely in the
sense of a forced guidance. Furthermore, this embodiment may have
an advantage that a risk of canting is reduced. The mounting on the
insert is expediently designed such that the guiding levers
connected in a hinged manner can only be fitted and separated if
the milling tool implement is not inserted.
[0037] An insertion guide is preferably provided on the guiding
plate and is formed in particular as a dovetail guide. The
different inserts of the ensemble as have been described
beforehand, can therefore be inserted easily and positioned
precisely with respect to the guiding plate.
[0038] The set of equipment advantageously further comprises a pair
of insertion tongs for the curved milling gauge. These tongs grip
the curved milling gauge with a form fit in a defined position, the
pair of insertion tongs cooperating via aligning lugs with the
aligning device such that the insertion tongs have a clear position
and therefore the curved milling gauge held with a form fit in a
clear position by the insertion tongs is also positioned clearly
relative to the guiding plate. The handling is thus simplified
considerably, since the curved milling gauge having generally
relatively large dimensions can thus be positioned safely and
precisely. An incorrect positioning is therefore ruled out.
[0039] The set of equipment expediently further comprises aligning
rods for lateral arrangement on the base frame in such a way that
they point away from one another. Aligning bores are provided on
lateral sides of the base frame for assembly of these aligning
rods.
[0040] The set of equipment further comprises a drill having a
depth stop. It is designed to create receptacles on the bone in a
positionally accurate and simple manner, said receptacles being
intended for anchoring pins of the endoprosthesis.
[0041] The set of equipment further comprises various awls for
broaching a concavity on the bone, in particular a medullary cavity
on the femur. It expediently further comprises a rasp/broaching
awl, of which the shaft has a recess. This is formed so as to
receive a stop plate, which in particular acts as a depth stop. The
rasp/broaching awl is expediently designed such that it has 2, 3 or
4 cutting edges. In this case, the teeth are arranged on the
cutting edges with a vertical offset relative to one another. As
the teeth are rotated, bone material is thus removed at various
points, such that the bone surface is smoothed.
[0042] The set of equipment expediently further comprises a
direction gauge, which is provided for positioning of the base
plate and which acts on the aligning device. In particular, it is
designed to act on the rasp/broaching awl inserted in the medullary
cavity, and therefore to position the base plate exactly with
respect thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] The invention will be explained in greater detail
hereinafter with respect to the accompanying drawings, in which an
advantageous exemplary embodiment is illustrated and in which:
[0044] FIG. 1 shows an illustration of a base frame;
[0045] FIG. 2 shows a reamer;
[0046] FIG. 3 shows elements for aligning the base frame;
[0047] FIG. 4 shows sawing and milling gauges for preparing a
hollow at the end of a femur;
[0048] FIG. 5 shows a slotted link milling gauge for fine machining
the hollow;
[0049] FIG. 6 shows tools for preparing a medullary cavity;
[0050] FIG. 7 shows a curved milling gauge comprising a main
body;
[0051] FIG. 8 shows a guiding piece for the curved milling gauge
according to FIG. 7;
[0052] FIG. 9 shows a condyle milling cutter inserted into the
guiding piece according to FIG. 8;
[0053] FIG. 10 shows a pair of insertion tongs for inserting the
curved milling gauge into the base plate;
[0054] FIG. 11 shows individual illustrations for arranging the
guiding piece on the main body of the curved milling gauge;
[0055] FIG. 12 shows an illustration of the kinematics of the
guiding piece on the main body;
[0056] FIG. 13 shows alternative embodiments of the guiding
piece;
[0057] FIG. 14 shows details for aligning the base frame;
[0058] FIG. 15 shows details for use of compensating pieces
according to FIG. 3;
[0059] FIG. 16 shows details for use of the milling cutter
according to FIG. 3;
[0060] FIG. 17 shows an alternative fastening of the spacers;
[0061] FIG. 18 shows details for use of the sawing gauge according
to FIG. 4;
[0062] FIG. 19 shows an alternative embodiment of the direction
gauge;
[0063] FIG. 20 shows a front view for use of the first milling
gauge with milling cutter according to FIG. 4;
[0064] FIG. 21 shows an alternative for use of the first milling
cutter;
[0065] FIG. 22 shows details for use of the second milling gauge
according to FIG. 4;
[0066] FIG. 23 shows details for use of the slotted link milling
gauge according to FIG. 5;
[0067] FIG. 24 shows an alternative slotted link milling gauge;
[0068] FIG. 25 shows securing devices for inserts; and
[0069] FIG. 26 shows illustrations of the cooperation between
securing devices and inserts.
DETAILED DESCRIPTION OF THE INVENTION
[0070] The set of equipment illustrated as an exemplary embodiment
in FIGS. 1-11 for implanting a knee joint endoprosthesis comprises
two awls 90, 91 (see FIG. 14) and a rasp/broaching awl 92 (see FIG.
2), a base frame 1, pins 99 as a fastening device for fastening to
a femur bone, an aligning insert 3, a frontal-sawing insert 40,
spacers 34, a feeler gauge 39, a first milling insert 4, a second
milling insert 5, a third milling insert 6 as a slotted link guide,
and a curved milling gauge 7 with a condyle milling cutter 85.
[0071] The base frame 1 comprises a guiding plate 12 and a primary
gauge 11 protruding orthogonally laterally therefrom. A first saw
blade guide 20, which is used to compensate for different condyle
heights, is formed on the primary gauge 11 in the upper region, and
a second saw blade guide 21, which is used to machine the condyles
with use of femoral segments, is formed on the primary gauge 11 in
the lower region. Furthermore, bores 22 for fastening pins are
formed in the region between the saw blade guides. In the region of
transition to the guiding plate 12, receiving bores 26 for spacers
are provided, aligned in the direction of extension of the guiding
plate 12.
[0072] The base frame 1 is provided in different sizes. In this
case, the distance between the reference plane 10 and the saw blade
guides 20, 21 and also the receiving bores 26 for the spacers is
identical for the different sizes.
[0073] The guiding plate 12 is formed with its underside as a
reference plane 10. This serves as a bearing surface for condyles
of the femur. A planarity is formed on the upper side and acts as a
tool plane 14. It is the reference plane for the different inserts
that are received on the guiding plate 12. In this case, the
dimension between the reference plane 10 and the tool plane 14 is
matched to the respective size of the implant to be inserted. A
linear guide 2 is arranged on either side of the tool plane 14 and
comprises two undercut edges between the tool plane 14 and the
upper side of the guiding plate 12. These act as a dovetail guide
for the inserts 3, 4, 5 and 6.
[0074] A milled recess 15 is formed on the guiding plate 12 on each
of the lateral sides. It is of such a depth that the breadth
remaining between said milled recesses corresponds to the width of
the width dimension of the implant associated with the respective
base plate 1. The milled recess 15 thus acts as a visual aid for
selecting the implant sizes. An aligning bore 23 with an inner
thread, which indicates the position by means of an aligning rod 38
to be screwed in, is provided in each milled recess 15. Bores 28
for fastening pins 99 are provided in a manner flanking the milled
recesses 15. In the central region of the guiding plate 12, a
central opening of an approximately rectangular basic shape is
formed, which on its two lateral faces pointing to the side acts as
a lateral delimitation 66 and by means of its edge 65' facing away
from the primary gauge acts as a rear delimitation for a milled
mortise recess. Guiding slots 17 for an insertion implement 76 of
the curved milling gauge 7 are formed in the lateral sides 66.
Drill guides 18 for a pin-hole drill are provided on either side in
the guiding plate 12 adjacently to said guiding slots. A posterior
saw blade guide 19 for condyle machining is formed in the rearward
region in the vicinity of the rear delimitation 65' for the milled
mortise recess. At the opposite end of the large central opening, a
diagonal changeover guide 16, 16' is formed in the end pointing
toward the primary guide 11 and is oriented parallel thereto. At
its respective side faces, said changeover guide has a double curve
shape and thus forms a bipolar receptacle for the frontal-sawing
insert 40. This is inserted in the position denoted by reference
numeral 16 for processing for a left-side position, and is inserted
in the positioning denoted by reference numeral 16' for machining
of a right-side implantation.
[0075] A central fastening 14 is provided centrally on the base
plate 12 above the primary gauge 11. Said fastening is used to
fasten the individual inserts. It is always located at the same
point on the base frame 1 for the different sizes, such that the
different inserts can be used without difficulty with base frames
of different size. Free spaces 29 are formed on either side thereof
and create the necessary clearance for fastening pins on the curved
milling gauge 7 for fastening thereof to the femur.
[0076] The rasp/broaching awl denoted in its entirety by reference
numeral 92 comprises a plurality of cutting edges 93 in its lower
region, which are each provided with a multiplicity of teeth 94. A
tooth-free region 95 with reduced diameter upwardly adjoins the
cutting edges 93 provided with the teeth 94. A recess is formed
thereabove. This recess serves as a receptacle for a stop plate 97.
The cutting edges 93 are preferably formed in a triangle
configuration, which means that three cutting edges 93 are
provided, which are arranged at an angular distance of 120.degree..
It is noted that a different number of cutting edges, in particular
two cutting edges or four cutting edges, could also be provided
(see illustrations in FIG. 2b). In the embodiment illustrated in
FIG. 2a, the arrangement of the teeth 94 is selected such that the
teeth 94 of a cutting edge 93 are arranged so as to be offset
vertically in relation to the teeth 94' of the adjacent cutting
edge 93', as measured from the tip of the rasp/broaching awl 92.
This has the advantage that, as the rasp/broaching awl 92 is
rotated, a more uniform shaping of the bone wall is achieved. It is
specially designed to preserve the bone in the region close to the
edge. For this purpose, it has a flattened portion, with which it
is oriented relative to the bone edge. After introduction into the
depth of the medullary cavity and after rasping, it is then used as
a reamer.
[0077] The rasp/broaching awl 92 acts via its upper shaft region
above the recess 96 as an aligning aid and cooperates with the
aligning insert 3 for this purpose. This insert has an opening 31,
which is open toward the side via a constriction 31'. The
rasp/broaching awl 92 can be introduced via its recess 96 into the
opening 31 by being inserted through the constriction 31'. A
relative positioning between the rasp/broaching awl 92 and the base
plate 1, in which the aligning insert 3 is inserted, is thus
achieved. The aligning rods 38 are screwed into the aligning bores
23 and in doing so indicate to the surgeon the position of the base
frame and thus act as an aligning aid. In the illustrated exemplary
embodiment, the opening 31 is not oriented orthogonal to the
reference plane 10, but is arranged at an oblique angle thereto.
The deviation from the orthogonal direction is denoted as a shaft
angle .alpha. and is a characterizing dimension for the prosthesis
(in the example 6 degrees). In order to allow the surgeon to
visualize this shaft angle, an opening 30 is also formed on the
aligning insert 3 and is formed on a pair of tongs protruding via
the front delimitation of the base plate 1, a tracer pin 30' being
plugged through this opening 30, being arranged outside the femur
to be machined, and therefore indicating to the surgeon the shaft
angle of the rasp/broaching awl 92 inserted in the medullary cavity
of the femur to be machined (see FIGS. 14b and c).
[0078] The aligning insert 3 is chamfered in a wedge-like manner on
its lateral sides 33 (wedge angle .gamma. is 4 to 10 degrees,
preferably 6 degrees), more specifically at least by the shaft
angle .alpha.. On the one hand, sufficiently accurate positioning
in the linear guide 2 is thus achieved, and on the other hand,
unlike with an actual dovetail guide, the insert can be removed
upwardly, more specifically at the end of the aligning process (see
FIG. 14).
[0079] It is noted that a concavity can be premachined in the
medullary cavity of the femur using a broach milling cutter 37,
which may possibly have a recess 37', similarly to the recess 96 on
the rasp/broaching awl 92, and can be inserted accordingly via the
constriction 31' into the opening 31 (see FIG. 16). The broach
milling cutter 36 is in this case tilted by the same shaft angle
.alpha. as the rasp/broaching awl 92. It is thus made possible to
mill out a deep region for the shaft of the prosthesis. The maximum
milling depth is limited in this case by a depth stop 37'' formed
as a shaft collar. The required erosion can thus be produced even
deep in the bone, more specifically at the correct angle, without
the need for specific skills on the part of the surgeon for this
purpose.
[0080] Generally, the base frame 1 will rest directly via its
reference plane 10 on the end of the femur. This is not always the
case however, but in particular in cases of reoperation and in
other cases, in which bone material is already absent (if it was
removed in a previous operation or is absent due to a defect),
spacers 35 can be arranged on the underside 10 of the base plate 1
(see FIG. 3). These are formed in pairs and are held via fastening
pins 36, which are inserted into the receiving bores 26, on the
primary gauge 11 of the base plate 1 (see FIG. 15a). They are
available in different thicknesses (see FIG. 15b), such that a fine
adjustment can be made herewith. Alternatives for the spacers are
illustrated in FIG. 17. The simplest alternative consists in
arranging adjusting screws at the edge of the base frame (see FIG.
17a). Alternative spacers 35, 35' for forming a base may also be
provided and are held with a form fit on the lateral sides via hook
connections or pin connections (see FIGS. 17b and c). These spacers
may also be provided in the lower region with pin openings through
which fastening pins 99 are inserted (see FIG. 17d).
[0081] If the position of the base frame 1 is then defined by means
of the aligning insert 3, the base frame is thus fixed relative to
the femur by introducing the fastening pins 99 into the openings
28. The aligning insert 3 and the rasp/broaching awl 92 can then be
removed. The aids used for positioning, in particular the aligning
rods 38 and the tracer pin 30', are likewise removed.
[0082] By means of a bone saw known per se and not described in
greater detail, the condyles at the dorsal end can then be machined
with use of the posterior saw blade guide 19 (see FIG. 18c). In the
next step, the frontal-sawing insert 40 is inserted into the
corresponding diagonal changeover guide 16, 16', more specifically
irrespective of whether the implantation is a left-side or
right-side implantation. The orientation given by the double
arc-shaped recess 16, 16' is defined by the bipolar fixing by means
of the slot 42, in each of the end positions 43, 43' of which a
fastening screw 13 is screwed into the central fastening 14. The
frontal condyle side is then machined along the V-shaped saw blade
guides 41, 41' by means of the bone saw known per se (see FIGS.
18a, b).
[0083] In the next step, the plane of rotation can then be fixed in
one direction by means of the feeler gauge 39, which is plugged
into the slot 27 on the base frame 1, and the plane of rotation in
another direction, oriented transverse to the first-mentioned
direction, can then be fixed by insertion into the sawing slot 40,
40'. The pivot point is determined by the point of intersection of
the planes of rotation. An alternative implement is illustrated in
FIG. 19. It comprises a bridge support as a direction gauge 39'
with indexings 39'' arranged on either side. The bridge support 39'
is inserted into receiving slots 17 on the base frame 1, and the
orientation of the base frame 1 can be set by the form-fitting
connection thus produced. The length of the indexings 39'' is
dimensioned such that they indicate via their end the respective
resulting position of the pivot point Z (see FIGS. 19b and c). This
enables quick alignment that can be easily checked.
[0084] In the following step, the first milling insert 4 is
inserted into the base frame 1 and is fixed by means of the central
fastening 14, which is accessible through an opening 44, and by
means of the fastening screw 13. The insert 4 has a large central
opening 45 with an upwardly protruding guiding sleeve 45' which
form a receptacle for a broach milling cutter 49. This has a collar
49' in its upper region, said collar cooperating with the upper
edge of the guiding sleeve 45' in such a way that a depth stop for
the broach milling cutter 49 is formed. Part of the concavity in
the medullary cavity necessary for implantation is thus created,
and on the other hand the wall left by the reamer is reduced in the
front region, defined in terms of its height (see FIG. 19). The
reduction of the height of the wall in the front region can
alternatively also be achieved by means of a chisel 46, as
illustrated in FIG. 20. The chisel 46 has a main body which, in
cross section, has the shape of a segment of a circular arc and, at
the rear end, has an impact head 46' also acting as a depth stop. A
guiding slot 47 complementary to the cross-sectional shape of the
chisel 46 is provided in the base frame 1 on the primary gauge
11.
[0085] In the following step, the first milling insert 4 is
replaced for a second milling insert 5. This has a double
receptacle 51, which is octagonal in cross section and forms two
receiving positions 52, 53 for a bulk milling cutter 59. The two
receptacles 52, 53 are not arranged centrally, but both with a
different offset in relation to the side (lateral offset). Each of
the two receiving positions 52, 53 is assigned an upwardly
protruding sleeve 52', 53'. The bulk milling cutter 59 in its upper
region likewise has a protruding collar 59', which cooperates with
the upper edge of the sleeve 52', 53' assigned to the respective
receptacle 52, 53 and thus forms a depth stop for the bulk milling
cutter 59 (see FIG. 22a). A large part of the cavity can thus be
preformed for the reception of the implant. It is noted that the
second milling insert 5, similarly to the first milling insert 4,
is positioned clearly on the base frame 1 by means of an opening 54
in line with the central fastening.
[0086] Due to the different depth stops of the two receptacles 52,
53 of the double receptacle 51, the cavity in the bone can be
efficiently broached. If this is not necessary, a simplified second
milling insert 5' can be provided and has a double receptacle 55
without lateral offset. Here, the depth stops may be arranged at
the same height however (see FIG. 22b); it is not to be ruled out
however that they are arranged at different heights (in accordance
with the illustration in FIG. 22a).
[0087] It is further noted that the second milling insert 5 is
contained in the set of equipment in two versions. One version is
for left-sided implantation, and a second version, which is axially
symmetrical, is formed for right-sided implantation (see the
milling inserts 5 in FIG. 4 marked by "L" and "R").
[0088] In the following step, the second milling insert 5 is
replaced by a third milling insert 6, which is formed as a slotted
link insert (see FIGS. 5 and 23a-c). This has two slotted link
windows 60, 61 oriented in a T-shaped manner and two inspection
windows 62, 63. The slotted link window 60 is formed as a slot and
acts as a receptacle for the fastening screw 13, by means of which
the slotted link insert is guided on the base frame 1. The slotted
link insert 6 can therefore be moved to and fro frontally and
dorsally. A slotted link slider 65 is inserted displaceably into
the transversely oriented slotted link window 61 and has a handle
64 with a receptacle 67 for a milling tool 68, 69. The milling
tools 68, 69 are a pre-milling cutter and an end-milling cutter,
which are designed for different milling depths by means of a stop
collar 68', 69' arranged at different distances from the tip (see
FIG. 5 and FIG. 23c). They can be inserted through a central
opening 67 in the handle 64 into the slotted link slider 63. By
moving the slotted link slider 63 along its slotted link window 61
and by moving the slotted link insert 6 along the slotted link
window 60 (x/y movement), a rectangular cavity cross section can be
milled out with high precision. Thanks to the precise slotted link
guidance, the cavity can be produced with high dimensional
accuracy, and the box-like receiving space for the knee prosthesis
can thus be prepared in the femur cavity.
[0089] An alternative embodiment for the slotted link insert 6 is
illustrated in FIG. 24. It is a hinged slotted link insert 6'. It
has two guiding levers 60', 61' hinged to one another. At one end,
they are mounted rotatably via a pivot pin 62' on a main plate of
the insert 6', and at the other end a receptacle 67' for the
milling tools 68, 69 is formed. A U-shaped slotted link path 63' is
cut out on the base plate of the slotted link insert 6', and the
milling tool 68, 69 inserted into the receptacle 67' is forcibly
guided in said path by the guiding levers 60', 61'. The pivot pin
62' is provided with a flattened portion 64', such that the guiding
levers 60', 61' can only be fitted thereon and removed therefrom in
a predetermined assembly position. The flattened portion 64' is
aligned here such that, in the assembly position, the receptacle
67' is arranged aside the slotted link path 63'. It is thus ensured
that the assembly and disassembly processes can only be performed
when the milling tool 68, 69 is removed.
[0090] An additional securing of the inserts 3, 4 and 5 in the base
frame 1 is illustrated in FIG. 25. The securing opening 14 on the
base frame is formed twice, more specifically once for the
left-hand side 14' and once for the right-hand side 14''. The
fastening openings 34, 44 and 54 on the inserts 3, 4 and 5 are
formed as grooves 34', 34'' running as far as the edge and offset
laterally with respect to one another, depending on whether the
respective insert is provided for left-side or right-side
implantation. A securing lever 66' comprises a toggle 66'' at the
end of a shaft stump. The securing lever 66' can be inserted in the
orientation illustrated in FIG. 25b into one of the fastening
openings 14', 14'' from the side. By moving the securing lever 66',
the toggle 66'' is moved through a right angle, whereby a locking
effect is achieved. In order to avoid accidental actuation of the
securing lever 66', a securing bolt 14''' is preferably provided
and is inserted into the base frame 1 from the side and rests in an
aligned manner against a flattened portion 66''' of the shaft
stump, in such a way that the shaft stump and therefore the
securing lever 66' are prevented from rotating. The securing lever
66' can then only be moved again when the securing bolt 14''' is
removed. The corresponding inserts are expediently provided on
their underside with an undercut bore 50' in the case of an insert
5' to be secured against lifting out (see FIG. 26a) and/or with the
groove 34', 34'' and a widened end in the case of an insert 3' to
be secured against displacement (see FIG. 26b). The open position
is illustrated in each of the two smaller images (at the top in
FIG. 26a and to the left in FIG. 26b) as well as the closed
position (at the bottom in FIG. 26a and to the right in FIG.
26b).
[0091] Once the box-shaped receiving space has been developed in
the femur, the sliding paths on the condyles are then machined.
Reference is made in particular to FIGS. 7 to 10. To machine the
condyles, the curved milling gauge 7 is used. It is inserted by
means of a pair of insertion tongs 76. The pair of tongs comprises
two tong halves 78, which, at their front ends, have two grippers
79 cooperating with a form fit with the curved milling cutter 7. On
the outer face of the tong halves, aligning lugs 77 pointing away
from one another are formed. They are designed such that they are
congruent to the shape of the guiding slots 17 on the base frame 1.
Precise positioning of the curved milling gauge 7 relative to the
base frame 1 is thus ensured by inserting the insertion tongs 76
into the base frame 1, the aligning lugs 77 engaging with a form
fit in the guiding slots 17 (see FIG. 10). It is noted that the
curved milling gauge 7 is available in different (preferably four)
sizes, the positioning by means of the insertion tongs 76 being
achieved similarly by form-fitting engagement in the guiding slots
17 irrespective of the size used.
[0092] The curved milling gauge 7 comprises a main body 70, of
which the basic shape corresponds approximately to a cuboid-like
box (see FIG. 7). Grooves 71 running vertically from top to bottom
are formed on the lateral sides of the curved milling gauge. The
grooves are used for sturdier and position-maintaining anchoring in
the cavity of the femur. On the upper side of the main body 70, an
upwardly protruding circular arc segment 72 is formed in one piece
and covers an angular range of approximately of 100 to 120 degrees
and, in the front region, is pulled down to approximately half the
height of the main body 70. In the region close to the edge, it has
a recessed guiding path 74 on one of its side faces. Said path is
delimited via a web 75 toward the upper edge of the circular arc
segment 72, wherein, in the downwardly pointing front region, an
extension 74' of the guiding path 74 is formed and is web-free. An
opening is thus created, through which a follower 84 of the guiding
piece 8 can be inserted into the guiding path 74 or removed
therefrom. This can occur only in the position when the follower 84
is located in the region of the extension 74. The guiding path 74
is closed at the other, rear end and forms a stop 76 for the
follower 84.
[0093] From a rear side of the main body 70, a double slit 77
extends as far as the upper side of the main body 70. A receiving
bore for a securing screw 79 is arranged transverse thereto. It
acts as a pivot bearing for a toggle linkage 80, of which the free
end protrudes from the main body 70 and which is pivotable along
the double slit 77 (see FIG. 7). At its free end, the toggle
linkage 80 carries a pivot pin 81, of which the cross section is
approximately rectangular with straight long sides and
circular-arc-shaped convex short sides (see FIG. 11a). Between the
circular-arc-shaped convex short sides, the pivot pin 81 has a
meridian of greatest width D, and between the straight sides a
meridian of smallest width d.
[0094] The guiding piece 8 is generally of T-shaped design with a
transverse segment 89 and a longitudinal segment 88 (see FIG. 8).
In each of the outer regions, a stepped bore 87 with a peripheral
shoulder is arranged on the transverse segment 89. Said stepped
bores are oriented with their axis 87' such that they form an angle
.alpha. from 75 to 85 degrees, preferably 80 degrees, to the
transverse segment 89. The axes 87' are therefore divergent. The
stepped bore 87 forms a guide for a condyle milling cutter 85,
which is inserted via a lateral opening 82 into the stepped bore
87. The condyle milling cutter 85 comprises a milling head and a
shaft, on which a cylindrical thickening 86 distanced from the
milling head is formed. Since it is placed on the peripheral
shoulder of the stepped bore 87, it delimits the milling depth.
[0095] The longitudinal segment 88 of the guiding piece 8 is
angled; it forms an angle from approximately 15 to 25 degrees,
preferably 20 degrees, to the plane spanned by the axes 87'. The
follower 84 is arranged laterally on the longitudinal segment 88
and guides the guiding piece 8 along the guiding path 74. At the
free end, the longitudinal segment 88 is formed in a fork-like
manner and is provided with a transverse bore, which acts as a
pivot bearing sleeve 83. It is open toward the free end via a
constriction 83'. The width of the constriction 83' is dimensioned
such that it is larger than the meridian of smallest width 82 and
smaller than the meridian of greatest width 82'. If the pivot
bearing sleeve 83 and the pivot pin 81 are oriented such that the
constriction 83' contacts the meridian of smallest breadth 82, the
guiding piece 8 can be pushed with its pivot bearing sleeve 83 onto
the pivot pin 81, and in any other orientation the pivot pin 81 is
prevented from passing through the constriction 83'. An angular
lock is thus provided, which can be opened and closed only in one
position and is otherwise locked (see FIGS. 11a and b).
[0096] The pivot pin 81 is oriented on the toggle linkage 80 such
that the guiding piece 8 can be coupled and removed only in an
elongate position when the guiding piece 8 forms a line with the
toggle linkage 80 (see FIG. 11a).
[0097] If the guiding piece 8 is coupled, it is inserted via its
follower 84 in the region of the extension 74' into the guiding
path, the guiding piece 8 being arranged at an angled position
(that is to say no longer elongate) relative to the toggle linkage
80. The pivot pin 81 is therefore prevented from passing through
the constriction 83'. The guiding piece 8 inserted into the guiding
path 74 is therefore locked securely to the toggle linkage 80 (see
FIG. 11b).
[0098] The kinematics thus achieved for the guidance of the condyle
milling cutter 85 is illustrated in FIG. 12 as a multi-phase
diagram. The pivot bearing 78 is illustrated at the bottom in the
middle of the image. It forms a fixed pivot point for the curve
guidance consisting of guiding path 74, guiding piece 8, and toggle
linkage 80. The guiding piece 8 is guided via its follower 84 over
the entire pivot range along the guiding path 74. The guiding path
74 has an increasing curvature (from left to right in the figure),
whereby the radial distance between the pivot bearing 78 and
follower 84 increases. As a result, not only does the condyle
milling cutter 85 inserted into the guiding piece 8 become
increasingly removed from the pivot bearing 78 (it thus describes
an arc becoming continuously greater), but it also changes its
orientation. Due to the articulation via the toggle linkage 80, the
guiding piece rotates, such that the axis 87 for the milling cutter
85 is directed toward the pivot bearing 78 at the start of the
pivot motion, but rotates increasingly dorsally (to the right in
FIG. 12) with the movement of the guiding piece 8 along the guiding
path. A condyle shape is thus produced on the bone by means of the
milling cutter 85, the current center of rotation of the milling
cutter not being stationary as the knee joint flexes, but shifting
dorsally. A path of movement that corresponds practically fully to
that of the natural knee and is therefore physiologically extremely
favorable is thus enabled for the knee prosthesis implanted using
the equipment according to the invention. Knee prostheses implanted
in this way provide the best preconditions for long-term therapy
success without the need for revision surgery after a short period
of time.
[0099] An alternative embodiment of the guiding piece for different
condyle milling is illustrated in FIGS. 13a and b. In this case,
guiding pieces 8', 8'' are provided and receive a horizontal
milling cutter 85', 85''. In the variant illustrated in FIG. 13a,
the horizontal milling cutter 85' is mounted from the side into the
guiding piece 8', and is mounted there in a one-sided manner. The
movement kinematics corresponds to that illustrated in FIG. 12. In
the variant illustrated in FIG. 13b, the toggle linkage and the
guiding piece 8'' are arranged externally, and the horizontal
milling cutter 85'' is inserted through the guiding piece 8''. In
this variant, it is necessary to reassemble the toggle linkage and
the guiding piece 8'' in order to machine the other side.
[0100] The equipment further comprises an awl set for creating and
preparing a prosthesis receptacle in the femur. The awl set (see
FIG. 6) comprises an access awl 90, which is used to open the
medullary cavity of the femur. By means of reamers 91, which are
preferably contained in the set in different lengths and diameters,
the medullary cavity is enlarged successively. The special
rasp/broaching awl 92 with the stop plate 97 is further provided
and has already been described above. Lastly, a pin-hole drill 98
with stop is provided and is inserted into the drill guides 18 in
order to form receptacles for anchoring pins (not illustrated) on a
condyle part of the knee joint endoprosthesis.
* * * * *